{
  "bibcode": "2015GCN.17917....1B",
  "body": "M.G. Bernardini (INAF-OAB), P. D'Avanzo (INAF-OAB), A. Melandri\n(INAF-OAB), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), A.\nAmaral-Rogers (U. Leicester), J.P. Osborne (U. Leicester), A. D'ai\n(INAF-IASFPA), A. Maselli  (INAF-IASFPA), D.N. Burrows (PSU) and P.A.\nEvans (U. Leicester) report on behalf of the Swift-XRT team:\n\nSwift-XRT has performed follow-up observations of the MAXI-detected\nburst GRB 150608A (Arimoto et al. GCN Circ. 17912) in a series of\nobservations tiled on the sky. The total exposure time is 3.1 ks,\ndistributed over 7 tiles; the maximum exposure at a single sky location\nwas 955 s. The observations started at T0+8.0 ks, and are entirely in\nPhoton Counting (PC) mode. \n\nAn uncatalogued X-ray source is detected in the data collected between\nT0+9.1 ks and T0+14.7 ks. This source is above the RASS limit and is\ntherefore likely the GRB afterglow. The position of this source is RA,\nDec=13.1663, -0.6442 which is equivalent to:\n\nRA (J2000): 00:52:39.90\nDec(J2000): -00:38:39.0\n\nwith an uncertainty of 3.6 arcsec (radius, 90% confidence).  This\nposition is 29.1 arcmin from the MAXI position.  The light curve is\nconsistent with a constant source of mean count rate 8.3e-01 ct/sec. \n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.78 (+0.28, -0.26). The\nbest-fitting absorption column is  9.8 (+8.3, -6.0) x 10^20 cm^-2,\nconsistent with the Galactic value of 3.8 x 10^20 cm^-2 (Willingale et\nal. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux\nconversion factor deduced from this spectrum  is 3.5 x 10^-11 (4.0 x\n10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     9.8 (+8.3, -6.0) x 10^20 cm^-2\nGalactic foreground: 3.8 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.78 (+0.28, -0.26)\n\nThe results of the XRT-team automatic analysis of the likely afterglow\nare at http://www.swift.ac.uk/xrt_products/TILED_GRB00045/index_2.php.\nThe results of the full analysis of the tiled XRT observations are\navailable at http://www.swift.ac.uk/xrt_products/TILED_GRB00045.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 17917,
  "createdOn": 1433802802000,
  "email": "grazia.bernardini@brera.inaf.it",
  "subject": "GRB 150608A: Swift-XRT afterglow detection",
  "submitter": "Maria Grazia Bernardini at INAF/Brera  <grazia.bernardini@brera.inaf.it>",
  "eventId": "GRB 150608A"
}